This invention relates to headrests for cab type vehicles such as pickup trucks, large trucks, semi-trailer tractors, some recreational vehicles and the like. Many such vehicles are not provided with headrests which would cushion the head of vehicle occupants in case of an impact on the truck which would cause a backward rearwardly directed momentum force on the occupant's head which would cause the occupant's head to impact on the rear window, or cause a whip-lash neck injury, or both. Such an impact and injury could occur in many circumstances, but, for example, a vehicle being struck from behind could cause the hazard just described. A significant hazard is the uncushioned impact of a person's head against the rear window glass. If the glass does not break, the hard surface can cause injury to the person's head. If the glass does break, there is the added hazard of cutting from the broken glass.
One problem with such headrests is the lack of room in which to mount such a headrest. Another problem is that such headrests obstruct the view of the occupants of the vehicle. Another problem is that such headrests are made of resilient materials.
Injuries to a vehicle occupant's head as described above are due to the person's head striking a hard surface. The inertia of a person's head can be measured in foot-pounds of energy at the relative velocity of the person's head with respect to the surface which impacts on the head. The critical relative velocity measurement is important, irrespective of whether the head or the surface is moving or stationary. The critical property of the cushion is that the energy of inertia be absorbed, and not be redelivered after the impact. Resilient materials by definition are elastic, and rebound with a measurable portion of the absorbed energy after the force of the impact by elastically recovering their original shape. Desirably, a headrest cushion should not be resilient (elastic) because greater injuries are probable if a persons head strikes a resilient cushion, then is bounced away, causing a greater impact than necessary than if the cushion were not resilient. Desirably a headrest cushion should deform plastically, not elastically. Plastic deformation is that deformation which is not recovered or regained after impact. Energy absorbed by plastic deformation is not rebounded and in case of a headrest will not bounce or redeliver the energy to a person's head after an impact. One advantage of the present invention is that the cushion effect distributes the impact forces over a much larger area of the person's head and over a larger area of the window glass. These for distributions reduce the contact pressure between the person's head and the window, resulting in greatly reduced injuries and reduced likelihood of breakage of the window glass.
M.S. Mazhar U.S. Pat. No. 4,607,886 discloses a truck headrest which adjustably attaches to the truck seat and provides small pads which are supported against the rear window.
D.R. Alexander U.S. Pat. No. 4,807,933 discloses a headrest which includes a unitary resilient body which extends from the seat above the window and is supported by the window frame above and below the window.
J.R. Perserfield U.S. Pat. No. 4,770,466 discloses a headrest including recessed suction cups for detachably attaching a resilient headrest to a support surface such as a rear window.
These and other attempts to provide a headrest for cab type vehicles have not provided a headrest which solves the problems listed above.